Question

Tìm x:

a. x² - 1 + (3-x) x = 5

b. 7 (2x - 5) - 5 (7x - 2) + 2 (5x - 7) = 6

c. \(\dfrac{2x-1}{3}+\dfrac{x-2}{2}=1\)

Answer 1

a) \(x^2-1+\left(3-x\right)x=5\Leftrightarrow x^2-1+3x-x^2=5\)

\(\Leftrightarrow3x-1=5\Leftrightarrow3x=6\Leftrightarrow x=\dfrac{6}{3}=2\) vậy \(x=2\)

b) \(7\left(2x-5\right)-5\left(7x-2\right)+2\left(5x-7\right)=6\)

\(\Leftrightarrow14x-35-35x+10+10x-14=6\)

\(\Leftrightarrow-11x-39=6\) \(\Leftrightarrow-11x=45\Leftrightarrow x=-\dfrac{45}{11}\) vậy \(x=-\dfrac{45}{11}\)

c) \(\dfrac{2x-1}{3}+\dfrac{x-2}{2}=1\Leftrightarrow\dfrac{4x-2}{6}+\dfrac{3x-6}{6}=1\)

\(\Leftrightarrow\dfrac{4x-2+3x-6}{6}=1\Leftrightarrow4x-2+3x-6=6\)

\(\Leftrightarrow7x-8=6\Leftrightarrow7x=14\Leftrightarrow x=\dfrac{14}{7}=2\) vậy \(x=2\)